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The silicon photonic wire evanescent field (PWEF) sensor platform offers the advantages of small sensor size, high levels of function integration, and low cost manufacturing that comes with the use of established semiconductor fabrication processes. The technology should be fully compatible with existing infrastructure in molecular analysis and research and the manufactured sensor array chip cost should be low enough that the chips can be considered disposable. Furthermore, since many applications require simultaneous monitoring of many different simultaneous binding reactions, the possibility of integrating tens or even hundreds of independent molecular sensors on a single disposable sensor chip is very compelling. We present an overview of our multiplexed photonic wire sensor chip and a reader instrument that allows up to 128 independent binding reactions to be monitored simultaneously. A complete photonic wire molecular biosensor microarray chip architecture and supporting instrumentation is discussed. This microarray system is used to demonstrate a multiplexed assay for serotyping E. coli bacteria based on polyclonal antibody probe molecules. A coherent detection scheme that enables direct read-out of the optical phase and an order of magnitude enhancement of sensitivity compared to conventional detection is also discussed. Finally, we present advances in Fourier-transform interferometer arrays for spectroscopic sensing. A planar waveguide Fourier-transform spectrometer with densely arrayed Mach-Zehnder interferometers is presented. Subwavelength gratings are used to produce an optical path difference without waveguide bends. The fabricated device comprises of an array of 32 Mach-Zehnder interferometers, which produce a spatial interferogram without any moving parts, yielding a spectral resolution of 50 pm and a free-spectral range of 0.78 nm. As a result of similar propagation losses in subwavelength grating waveguides and conventional strip waveguides, loss imbalance is minimized and high interferometric extinction ratio of -25 to -30 dB is obtained. Furthermore, phase and amplitude errors arising from normal fabrication variation are compensated by the spectral retrieval process using calibration measurements., 2014 16th International Conference on Transparent Optical Networks (ICTON), 6-10 July 2014, Graz, Austria

The exact cause of Alzheimer's disease and the part played in it by aluminum is still speculative. We have studied serum aluminum in 356 healthy people, and we have observed that serum aluminum concentration is increased in aging people in relation to age. We suggest that this could be associated with an enhanced gastric permeability or by an increase in metal accumulation proportional to age. We have measured serum aluminum levels in patients with probable Alzheimer's disease, patients with other senile dementias, and age-matched group. Patients with probable Alzheimer's disease have statistically significant higher serum aluminum levels than patients with other types of senile dementias (alcoholic, vascular, multi-infart) and an age-matched control group. When we compare serum aluminum of patients with senile dementias from other causes with the age-matched control group, we do not find significant differences.

The authors present a mathematical formalism for studying the behaviour of the total kernel of the Fresnel integral describing the diffraction of light by a cascaded linear system. The optical system is formed by an arbitrary number of optical devices with small aperture pupils and small axial thicknesses. The total diffracted field is formulated in the Fresnel regime. The boundary value problem and the convergence behaviour of the kernel are analysed. Numerical results are given for the spectrum of the kernel of certain systems of interest, namely, circular aperture, slit aperture, apodizing aperture pupil and grid aperture. The possibilities for a quantum representation in terms of Lie algebra operators are explored.

A programmable digital circuit typically consists of a microprocessor, a memory device, an input data device and an output data device, with its corresponding communication busses. These devices work following a program which is stored in the memory device, as codified instructions. An opto-electronic system that emulates a programmable digital circuit is proposed and described in this work. This circuit is commanded by a sequential program stored as a spatial distribution of Fourier Holograms into a photorefractive crystal. The sequential program is conformed by instructions, which have been codified as binary pixels maps. To read and decode each instruction, the spatial position of the photorefractive crystal must change; and then a CCD camera captures the output image of the Fourier Hologram. Our LabVIEW software decodes the instruction from the captured output image and it commands the circuit to realize the decoded instruction. This software controls the CCD camera and an electromechanical system which moves the spatial position of the photorefractive crystal. The electromechanical system is continuously in communication with a PC through our software. This is because the electronic circuit of the electromechanical system, moves three stepper motors; depending on the position in which the crystal needs to be to read the next instruction. The experimental results and the complete description of the practical advantages and disadvantages of the complete engineering system and the emulation of the opto-electronic programmable digital circuit will be described in this work.

We introduce the gyrator transform which produces a rotation of two‐dimensional signal in phase space. Main properties of this transform are considered. The flexible optical set up for gyrator transform experimental implementation is discussed. The applications of the gyrator transform to image processing such as filtering, noise reduction, encryption are demonstrated.

In the Spanish Autonomous Community of Aragon, with about 1.200.000 inhabitants, there are currently 314 patients suffering from chronic renal failure (CRF). They are undergoing hemodialysis in 7 public hospitals. These centers centralize their controls of the aluminum (Al) levels in the patients’ sera and in the fluids used for dialysis in the “Unidad de Metales del Servicio de Bioquimica” of the Miguel Servet Hospital.

In a few earlier communications, spatial-transverse-impulse response (STIR) associated with the initial field transversely distributed across the entrance pupil of an inhomogeneous optical wave guide (photoreceptor) has been investigated. In the present work, effects of indetermination in the location of the origin on an arbitrarily defined refractive index profile, representing the degree of inhomogeity at the aperture pupil of a single receptor, have been studied. Some consequences related to a few possible technical applications have been discussed.

An exact treatment of the initial field falling on the entrance face of a photoreceptor, so that the scattered field far from the latter vanishes, is presented. Its physical interest and some consequences are discussed. By establishing certain similarities between the behaviour of the photoreceptor as light penetrates into and propagates along, and an optical linear system, it is possible to define a spatial transverse impulse response containing information on the diffraction capability of each individual receptor. The distribution of this function across a transverse plane depends upon the particular form of the refractive index in the photoreceptor. Thus, certain differences are seen to occur between the case of an homogeneous receptor and an inhomogeneous one, for particular values in the degree of inhomogeneity. This fact allows to interpret the presence of inhomogeneities in the photoreceptor structure.

The Optical Transfer Function of a flexible conventional fibroscope to be used for "in vivo" image transmission has been calculated and numerically analized through available experimental data. The results are derived from an earlier generalized study for gradient index optical media. A criterion to determine the image quality is established and discussed

We present here numerical estimates of the density and flux of energy based on physical parameters associated with the absorption properties of certain types of absorbing optical waveguides. These results are based on a theoretical formalism established previously for the initial field incident upon the entrance pupil of an absorbing optical waveguide. Based on these results, the mechanisms of confined energy transmission and possible cross talk between neighboring waveguides are discussed. Some comments on the behavior of Bessel functions with complex arguments are also included in the discussion.

A three-dimensional analysis of bending losses in dielectric optical waveguides is presented. It constitutes a nontrivial generalization of previous two- and three-dimensional studies by other authors. Our analysis is based on homogeneous integral equations for the total radiation field and suitable asymptotic approximations for Green’s functions. A key role is played by a new three-dimensional approximation for a relevant Bessel function with large order and argument (the former being larger than the latter). A nontrivial check of the consistency of all those approximations is given. General formulas are presented for the radiated field and the energy flow and for a bending-loss coefficient in three dimensions. Numerical results are also given, in order to assess the difference between the results of other authors and ours. Such a difference is rather small for monomode behavior near cutoff, increases as the behavior of the waveguide changes from monomode to multimode, and decreases as the parameter V increases for a given core radius and propagation mode.

The authors present a mathematically exact formulation of the initial field striking the aperture of an absorbing optical waveguide, via an integral equation description. An analysis of the residual scattering by the waveguide is presented. Because of the presence of the non-negligible absorption coefficient, the solution for the fraction of the confined power is obtained by performing non-trivial integrations of Bessel and Hankel functions with complex arguments. In order to carry out a numerical analysis a specific computational method is applied by using an approximated polynomial expansion whose validity is also discussed.

We outline ,a systematic procedure for formulating the general transfer function of a compound optical system working in the Fresnel regime.

For pt.I see ibid., vol.17, p.475 (1984). The possible confined propagation of slow (thermal) neutrons along cladded waveguides of small cross section (fibres) is studied, in order to improve a previously published analysis. Quite suitable possibilities for the core of the waveguide could be either Al or Si (or vacuum), so as to allow for confined propagation of neutrons along reasonable lengths, without large scattering and absorption losses. Tentative possibilities for the cladding could be either Ni or Fe. The bending losses are analysed for a curved neutron fibre in two spatial dimensions. Such bending losses turn out to be completely negligible, except in the case of a small radius of curvature Rc. To quote some typical values, for any fibre diameter between 0.1 and 1 mu m and reasonable lengths for it (between 5 and 10 cm), bending losses can be neglected other than for Rc

It is known that the cones and rods of the retina have directional sensitivity. For a normal observer, in the absence of aberrations like myopia, astigmatism, etc. the light entering the pupil of the eye is directly focussed on the retinal plane by the optical system of the eye. There, in the retina, the cones and the rods are regularly distributed in different retinal regions forming a mosaic structure. It is very well established from the earlier works of Enoch, (1), that both types of optical photoreceptors act as optical waveguides. This behaviour can be accounted for due to their special optical properties allowing conditions for total internal reflections inside its structure. At the time of the confinement of the energy inside each single receptor an important phenomenon of orientation takes place as well. In this work, we wish to establish that the various effects arising out of this phenomenon can be interpreted in terms of a possible apodising action of the eye.It will be shown that an improvement in the resolution of the retinal image detection is possible by comparing the human visual system with an apodised optical system. For that purpose we have established a linear array model for a section of the fovea, ( all receptors having the same geometry and optical properties ), then, we have calculated the distribution of the density of energy captured in this particular section of the retina, by assuming that the receptors are acting as monomode optical waveguides.The orientation mechanism is also considered, by including an inclination factor affecting each single receptor. We have compared the so obtained distribution to the one associated to a single receptor© (1987) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

An exact formulation of the electromagnetic field striking an optical waveguide is presented and compared with the decomposition relationship used in the literature. The expression for the critical angle is derived as a natural consequence of this formulation. Equations for the total fraction of power confined within a waveguide are derived and analyzed for the special case of absorbing waveguides. An explicit expression is derived for the fraction of energy confined within a waveguide supporting two sets of modes.